Polyphase supply circuit and frequency meter



J y 22, 1952 J. H. ANDRESEN, JR., ETAL ,60 0

POLYPHASE SUPPLY CIRCUIT AND FREQUENCY METER Original Filed Oct. 19, 1946 2 SHEETS-SHEET l IN V EN TORS y 22, 1952 J. H. ANDRESEN, JR., ETAL 0 ,520

POLYPHASE SUPPLY CIRCUIT AND FREQUENCY METER Original Filed Oct. 19, 1946 2 SHEETSSHEET 2 INVENTOR.

Patented July 22, 1952 POLYPHASE SUPPLY CIRCUIT AND v FREQUENCY METER John H. Andrescn, Jr., Port Washington, and Edward Kasner, Brooklyn, N. Y., assignors, by mesne assignments, to Kollsman Instrument Corporation, Elrnhurst, N. Y., a corporation of New York Original application October 19, 1946, Serial No. 704,512; now Patent No. 2,472,507, dated June 7, 1949. Divided and this application Novemher 1948, Serial No. 58,566

4 Claims. 1..

This invention relates to an, improved form of electronic circuit for producing a polyphase output from a Single phase inputand, mor particularly, to a, frequency meter utilizing such a circuit to measure the: input frequency.

One-object of theinvention is the provision of a frequency meter for measuring the frequency of a single phase input from a polyphase frequency/meter fed by an electronic circuit producinga twoephase output from a singlephase input with the individual: phases of the output substantially equalized over a lwide range of frequency;

Another object of this invention is the provision of a frequency meter for measuring the frequency of a single phase input from a polyphase frequency meter fed by an electronic circuit producing a two-phase output from a single phase inputwith the output frequency a sub-multiple of theinputf-requency'.

Another object of the invention is a simplified electronic circuit for producing a two-phase output from a single phase input, with the-individual phases of the outputsubstantially equalized over awide range". I

Another object of the invention is a frequency meter embodying a polyphase synchronous motor driving a drag cup tachometer with the motor fed from a: single, phase source Whosefrequency. is to be measured through an electronic frequency divider.

A further object is a frequency meter in accordance with the preceding object in which the electronic circuit provides a. polyphase' output having-afrequencywhich is a submultiple of the input frequencyto extend the range of frequency over which th meteris responsive.

This application isa divisional of the application, Serial No. 704,512, filed October 19, 1946, for Polyphase Supply Circuit and Frequency Meter, now Patent No. 2472,50? granted June 7'7, 1949."

Other; objects and features of the invention will be readily apparent to-those skilled'in the art from the specification and appended-drawings illustrating certain preferred embodiments in which:

Figure 1 is a; wiring diagram of. an electronic circuit and frequency meter according to the present invention, in which the frequency of the single phase input is divided inthe two phase output which feeds; a synchronous motor, driving a drag cup tachometer indicator.

Figures 2', 3, 4, 5 and 5' are representations of 8 and by-pass condenser 9.

2 the wave form outputs of various tubes of the circuitof Figure 1.

Figure 7 is a wiring diagram of a simplified form of frequency meter and electronic circuit providing for the two phase output from the single phase input but without frequency divi- SlOIl.

In the diagram of Figure 1, the single phase input is applied at I and 2 and isfed through a. protective resistor 3 to the control grid 4- of a voltage amplifying triod 5.v The wire 2 is connected toground and across I and 2 is provided a grid resistor; 6. The cathode I ofv the triode 5 is connected to ground through cathode resistor The anode II of the triode 5-is connected tothesupply through the load resistor l2.

The supply is. provided. from an alternating current source to, the supply transformer primary I3,,having secondary filament windings I l' and. I5 and a main winding. I6 supplying direct current through the rectifier tube I! and the filter circuitrepresented by the inductance I8 and condensers I9;

The amplified'output of the triode 5 is con nected through a couplingcondenser' 2I and grid limiting, resistor' 22' to the control grid 23' of a pentode' 24; the grid resistor beingindicated at 25. The pentode 24' and its circuit serve as an" amplifier-limiter which not only further amplifies the output Of'tri0de'5 but produces a square wave output. The pentode'i l has a screen grid 26' connected through by-pass condenser 27 to ground and through the voltage dropping resistor- 28'to the'supply. The suppressor grid 29 of the pentode 24 isconnected to the cathode 3I' and these are connected to ground and through a. condenser 32 to the supply, the condenser 32 and resistor 33 constituting a decoupling 'filter to suppress alternating current on the dividers to be hereinafter described.

circuitsincludes resistors 49., ll, 42,143 and resistors 44,15", 46; 4 which resistors form voltage dividing circuits which impress the grid bias, on thetubes- 3B, 39.- Condensers 48; 49-parallel the resistors 45; and; Anodesil and 52 of tubes- 38rand13'9 are connected to th supply through the resistors 46', 4'! and; 43, respectively. The

cathodes 5.3 and Stare connected to ground through cathode resistor 55 and by-pass condenser 56.

The output of tube 39 is fed through coupling condensers 5'! and 58 to the grids of tubes 59, SI forming with their circuit connections a second Eccles-Jordan frequency divider circuit similar to that previously described in detail for the circuit embodying the tubes 38 and 39. Similarly, the output of tube 38 is fed to a third Eccles- Jordan circuit embodying the tubes 62 and 63. The outputs of tubes El and 53 are suitably amplified and fed to the frequency responsive meter.

The amplifiying circuit is represented by the coupling condensers 64 and 65, grid resistors 66 and 61, screen grid resistors 08, screen grid bypass 69, tetrodes II and I2, load resistors 73 and I4, cathode resistor I5 and cathode by-pass condenser IS. The amplified output of tubes II and '12 is fed through coupling condensers TI and "I8 to the two phase windings '19 and 8| of a synchronous motor 82 driving a permanent magnet 83 within a conducting drag cup 84 which carries a pointer 85 cooperating with a dial 80. The drag cup and its shaft are provided with a biasing spring, not shown, limiting its displacement.

In the operation of the electronic circuit and of the frequency meter of which it forms a part, the input frequency applied at l and 2 may have any wave form but the unknown frequency should be periodic. This single phase input is amplified by the tube 5 and the output fed to the amplifier-limiter tube 24 whose output is further amplified and is in the form of a rectangular wave as shown in Figure 2, regardless of the input wave form. The frequency of the output of tubes 38 and 39 is one-half that of the input frequency and is in the form illustrated in Figures 3 and 4, being 180 apart. This frequency division is a well known characteristic of the Eccles-Jordan circuit which tends to drive one tube toward cutoff and the other toward saturation. With the application of the square wave form input, sharp pulses are applied to the grids. When a positive pulse appears, the tube in the circuit momentarily conducting undergoes no change. The non-conducting tube attempts to conduct but is prevented from doing so by the negative bias impressed upon it by the other tube. When a negative pulse appears at the grids, both tubes are momentarily driven to cutoff. The charges existing on the condensers 48 and 49 now exert control of the circuit and the higher charge across the condenser at the initially conducting tube causes the initially non-conducting tube to conduct heavy and drive the initially conducting tube to cutoff. One input cycle causes one transfer of conduction to produce the one-half frequency output.

The Eccles-Jordan circuits formed by tubes 59, 6| and 62, 63 further divide the outputs of the tubes 38, 39. The outputs of tubes 59, BI are 180 apart and the outputs of tubes 62 and 63 are 180 apart. However, the outputs of the tubes BI and 53 are only 90 apart as is shown by the wave form of Figures and 6, since the initial 180 out of phase relation of the wave forms of Figures 3 and 4 becomes 90 upon the frequency division. The output of tubes GI and 63 is amplified in the circuit including the tubes II and I2 and feeds the two phase synchronous motor 82 which thus rotates at a synchronous speed of one-quarter the input frequency.

The magnetic drag cup tachometer has a direct reading dial indication corresponding to the speed of the motor 82. The permanent magnet 83 is driven in synchronism with the motor 82 and sets up eddy currents in the drag cup motor 84 producing a shaft torque proportional to the speed of magnet rotation. This torque acting against a spring in known manner produces a displacement of the drag cup shaft proportional to the torque. The pointer mounted on the shaft indicates on the dial 86 the input frequency, the dial 85 bearing indicia calibrated in cycles per second.

The circuit, according to the present invention, not only provides for a two phase output from a single phase input but subdivides the input frequency to any degree desired since any number of frequency dividers may be placed in advance of the divider circuit represented by the tubes 38, 39 to subdivide the frequency to any desired degree. Hence, the range of the frequency meter is independent of the physical limitations of the synchronous motor. Thus, a synchronous motor having an accurate frequency response over a range of 10 to 150 cycles per second may, by a frequency subdivision of four, be utilized to operate a frequency meter indicating from 40 to 600 cycles per second and with further division, the range can be further extended as desired. The use of the two phase synchronous motor is greatly preferred for its efiiciency and good starting characteristics.

To secure the proper phase relation for continuous motor rotation in the same direction, it is desired that the firing order of the last dividers shall be consistent. Variation in the firing order of the dividers feeding thereto is immaterial since the reversal of both phases does not affect the direction of rotation. To secure the consistent order of firing in the last two dividers of the circuit, their plate load resistors are unbalanced so that the sections with the lower load resistances are always out in first to insure consistency in the firing order and proper rotation of the motor at all times.

The frequency meter and circuit of Figure 7 is a simplified form which may be utilized over a range of frequencies within the physical limitations of the motor, no provision being made for frequency subdivision in the output. In this circuit the single phase input is applied at IOI, I02 and across the input is connected a condenser I03 and resistor I04 with the impedance of the condenser I03 high with respect to the resistor I04 so as to secure a phase shift of almost to the grid I05 of tube I06. The anode I01 of tube I06 is connected through load resistor I08 to the supply and the cathode I09 is connected through cathode resistor III and by-pass condenser II2 ground. The output of tube I06 is connected through coupling condenser II3 to the grid H4 or tube II5 whose anode H6 is connected through load resistor I I! to the supply and whose cathode H8 is connected through cathode resistor H9 and by-pass condenser I2I to ground. The output of tube I I5 is fed through a coupling condenser I22 to one phase I23 of a two phase synchronous motor I24.

Potentiometer I25 is connected across the input parallel with I03, I04 and has an adjustable tap I26 feeding the grid I21 of tube I28 whose anode I29 is connected through load resistor I3I to the supply and whose cathode I32 is connected through cathode resistor I33 and by-pass condenser I34 to ground. The output of tube I28 is fed through coupling condenser I35 to the grid I36 of tube I31 whose anode I38 is connected through 'load'resi'stor [3.9. to the supply and whose cathode I4I is connected through cathode resistor I42 and by-pass. resistor I43 to ground. The output of tube I3! is fed through coupling condenser I44 to the second phase I45 of the synchronous motor I24. I46 and I4! are grid resistors for tubes. I31 and I I5.

The reactance ofv condenser: Iil3lis made high with respecttothe resistance. Hi4v to secure substantially a 90 phaseshiftto feed the gridof tube I06. The reactance of. condenser I35 is high at low frequency withrespect to the reactance of condenser I I3. As the input frequency increases, the reactance of condenser I35 has a greater effect to increase the grid voltage of tube I3! than does the change in reactance of condenser H3 upon the grid of tube II5. This effect serves to render the two phase output of the electronic circuit more nearly equal over a Wide frequency range. Without this effect, upon increase in frequency, the output of tube I I5 would increase without increase in the output of tube I37 to unbalance the input to the motor.

In the operation of the circuit, the adjustable tap I is located to equalize the inputs to tubes I28 and I26 at minimum input frequency. As the input frequency is increased from the minimum, the reactance of condenser I03 decreases and this results in an increased grid voltage on tube I06 which is in turn reflected by an increased voltage on the grid of tube I I5 with a corresponding increase in the input to phase I23 of motor I24. To counteractthis unbalance, the increase in frequency also lowers the initially high reactance of condenser I to increase the voltage polyphase output from a single phase source and for maintaining the individual phases of the output substantially uniform over a relatively wide range of frequency. This output interpreted through the synchronous motor and drag cup tachometer provides a simple and accurate measurement of the input frequency within the frequency range of the physical limitations of the synchronous motor.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. In a meter for measuring the frequency of a single phase voltage source, a limiter circuit in which said source is changed to a single phase of the same frequency but of rectangular wave form, a frequency divider circuit fed by said single phase square wave form voltage and producing a pair of voltages of one-half the initial frequency displaced 180 in time phase relation, a second frequency divider to which one of said half frequency voltages is fed, a third frequency divider to which the other of said half frequency voltages is fed, said second and third frequency dividers each producing a pair of voltages of onequarter the; initial inputfrequ'ency, meansifor supplyingone onlyofeach: of said second-and third frequency. divider outputs to produce atwo' phase voltage-.spacedQO? in timephase relation, a two phasesynchronous motor'fed from said two phase supply, amagnetic tachometer drivenby said synchronous motor and-including a pointerwhose displacement is proportional. to the speed of the motor, and calibratedindicia of frequencywith which said pointer cooperates to indicate the frequency-of the cum V In a meterformeasuring the frequency of a single phase voltage source, a first frequency divider circuit including a pair of electronic tubes fed from said source and having their output voltages of half the input frequency and spaced 180 in time phase, a second and third frequency div der each employing a pair of electronic tubes and fed from the outputs of the tubes of said first frequency divider, the outputs of the tubes of said second and third frequency divider having a frequency one-quarter that of the input voltage, a circuit connected to the output to one of the tubes of each of said second and third frequency dividers to produce a two phase output in said last mentioned circuit having voltages spaced in time phase relation, a two phase synchronous motor fed from said circuit, a magnetic tachometer driven by said synchronous motor and including a pointer whose displacement is proportional to the speed of the motor, and calibrated indicia of frequency with which said pointer cooperates to indicate the frequency of the source.

3. In a, meter for measuring the frequency of a single phase voltage source, a first frequency divider circuit including a pair of electronic tubes fed from said source and having their output voltages of half the input frequency and spaced in time phase, a second and third frequency divider each employing a pair of electronic tubes and fed from the outputs of the tubes of said first frequency divider, the outputs of the tubes of said second and third frequency divider having a frequency of one-quarter that of the input voltage, a circuit connected to the output to one of the tubes of each of said second and third frequency dividers to produce a two phase output in said last mentioned circuit having voltages spaced 90 in time phase relation, means for insuring a consistent order of firing of the tubes in said second and third frequency divider to maintain the proper time phase relation in said two phase output, a two phase synchronous motor fed from said two phase output, a magnetic tachometer driven by said synchronous motor and including a, pointer whose displacement is proportional to the speed of the motor, and calibrated indicia of frequency with which said pointer cooperates to indicate the frequency of the source.

4. In a meter for measuring the frequency of a single phase voltage source, a first electronic tube fed from said source and having its output voltage of the same frequency as the source but of rectangular wave form, a first Eccles-Jordan frequency divider circuit fed by said rectangular wave form voltage and having its output two voltages of subdivided frequency spaced 180 in time phase, a pair of Eccles-Jordan frequency divider circuits each fed by one of the output voltages of said first Eccles-Jordan circuit and producing output voltages of further subdivided frequency, a circuit fed by two only of the four outputs of said pair of Eccles-Jordan circuits to 7 produce a two phase output of subdivided fre- REFERENCES CITED quency Spaced 900 m phase relation two The following references are of record in the phase synchronous motor fed from said two phase file of this patent: output, a magnetic tachometer driven by said synchronous motor and including a, pointer whose 5 UNITED STATES PATENTS displacement is proportional to the speed of the Number Name Date motor, and calibrated indicia of frequency with 1,068,111 Crain July 22, 1913 which said pointer cooperates to indicate the 1,762,725 Marrison June 10, 1930 frequency of the source. 1,894,455 Youhouse Jan. 17, 1933 10 2,211,543 Kollsman Aug. 13, 1940 JOHN H. ANDRESEN, JR. 2,232,789 Kollsman Feb. 25, 1941 EDWARD KASNER. 2,425,811 Kent Aug. 19, 1947 

